Aseismic support structure

ABSTRACT

Disclosed is an aseismic support structure having one end secured to a fixed floor and another end connected to a subject structure placed on a floating floor. The aseismic support structure includes a toggle bar, an attachment section and a mounting section. The toggle bar has a universal joint at each end and is adjustable in its length to have a predetermined length. The universal joints are rotatable around axes in the horizontal and vertical directions, respectively. The attachment section is connected to the toggle bar through one of the universal joints, and has at another end a third universal joint comprising a vertical rotation section. A cantilever extends substantially parallel to the fixed floor, is connected to the attachment section by the third universal joint at one end and has a fourth universal joint at another end. The mounting section is connected to the cantilever by the fourth universal joint and secures the equipment.

This is a continuation-in-part of U.S. parent application Ser. No.08/570,789 filed Dec. 12, 1995 which claims foreign priority of Japanesecounterpart application 7-042747 filed May 2, 1995. Thiscontinuation-in-part also claims foreign priority of Japanesecounterpart application 7-254826 filed Oct. 2, 1995; and Japanesecounterpart application 8-30211 filed Feb. 2, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to aseismic support structuresfor supporting another structure on a fixed floor and more particularly,to an aseismic support structure which prevents equipment which issensitive to vibration (such as computer equipment) from being damaged,losing data or malfunctioning due to an earthquake.

2. Description of Related Art

There are a wide variety of structures that are presently utilized forindustrial applications such as manufacturing machines, home electricappliances, and transport equipment. Some of them are particularlysensitive to vibrations due to an earthquake. It is the primary objectof an earthquake resistant support structure (hereinafter called the"aseismic support structure") to prevent such structure from fallingdown when an earthquake occurs. In addition, devices which are sensitiveto the vibration of an earthquake such as electronic equipment,computers, instruments (hereinafter called the "equipment") should beconsidered when designing an aseismic support structure sinceearthquakes can cause such equipment to lose data, malfunction or bedestroyed. Severer requirements are imposed on equipment which observesearthquake behavior and immediately calculates data based on the resultsof the observation. To this end, it is necessary to secure suchequipment on a floor or the like by a structure which is different froma normal structure and which is an aseismic structure or a structurehaving high earthquake resistance.

A problem first encountered when an earthquake occurs is that theequipment moves or falls down. If equipment moves, attached cables orthe like may be damaged or contact other equipment so that thepossibility of malfunction is further increased. If the equipment fallsdown, it may be physically damaged, physically damage other equipment orinjure an operator. It is also very important that the vibrations causedby an earthquake not impact the interior of such equipment from thefloor. For example, vibrations can cause stress to occur in componentsin the equipment, leading to destruction of a package, error or loss ofdata.

Generally, because a number of cables are attached to the equipment, thefloor is constructed as a dual structure for large equipment. In otherwords, a free access floor is installed with a predetermined spacingover a fixed floor (slab) constituting the bottom so that free wiring isassured by utilizing the spacing.

There have been several support structures and approaches designed forapplications such as large equipment installed on dual-structuredfloors. The simplest approach is to mount casters on the equipment andplace it on the free access floor. Typically, in this approach, thecasters are normally fixed because problems can occur if the equipmentmoves during normal use. If an earthquake occurs and acceleration at apredetermined magnitude or more acts on the equipment, the casters arereleased for free movement so that the movement of equipment with thecasters absorbs the energy of the earthquake. This approach is thesimplest measure against an earthquake because only small parts(casters) are mounted on the bottom of the equipment and it can beconveniently relocated. However, it has earthquake resistance as low as0.4 G and cannot provide resistance for large earthquakes which causeserious problems with the equipment. In addition, it still has problemsof generation of stress on cables due to movement of the equipment andfalling-down of the equipment so that it is not a suitable approach asan aseismic support method. An improved method includes mounting a padon the caster and securing the equipment on the free access floor withsuction cups. However, they are not essentially appropriate in view ofearthquake resistance.

Another approach for improving earthquake resistance includes anapproach directly securing the equipment on the fixed floor (slab) orthe free access floor with means such as bolts. The former is alsocalled a direct support type, while the latter is called an indirectsupport type. The direct support type has an earthquake resistance whichcan withstand 1 G of acceleration or more and, accordingly, has anadvantage that the equipment does not move or fall down. However,because once the equipment is secured, it becomes difficult to be moved,this approach requires a long term perspective in the installationlayout for the equipment, and high costs are associated withinstallation. Moreover, as the earthquake's energy is directlytransmitted through the fixed floor, it is an approach which issusceptible to malfunction. There is an improved structure for suchaspect in which a resilient vibration absorber is disposed between thesecuring means and the equipment (PUPA 3-11699). However, it still failsto overcome problems such as workability and relocation of theequipment. The indirect support type imposes similar problems. Inaddition, aseismic construction of the free access floor is aprerequisite in employing such an approach which results indisproportionately high costs relative to the total cost.

A vibration isolation floor system that has been developed to solve someof the disadvantages of the above-described structures and approaches isdisclosed in PUPA 3-235873. This vibration isolation floor system is asystem wherein the entire floor of a room in which the equipmentincluding a computer is installed is supported by vibration absorptionmeans such as springs so as not to directly transmit the earthquakeforce to the equipment. An example is shown in FIG. 5. In the figure,there is an intermediate support 20 constrained by springs 101 and 103for x and y directions between a fixed floor 1 and a free access floor2. The free access floor 2 is connected to the intermediate support 20through the vertical spring 101 and a damper 102 so that the vibrationof an earthquake is not directly transmitted to the free access floor.In addition, as the fixed floor 1 is joined to the intermediate support20 through the horizontal spring 103 and a damper 102, the intermediatesupport 20 also does not significantly move in the horizontal directionso that the position of the equipment 100 is stabilized.

This system can reduce the impact of an earthquake on the equipment(reduce the possibility of malfunction and data error) in that it doesnot directly transmit the earthquake force to the equipment on the freeaccess floor. In addition, because the equipment can be simply securedon the free access floor, there is little possibility of the equipmentmoving or falling-down from the synergism with the earthquake resistanceof the free access floor. Moreover, since it is sufficient to secure theequipment by temporary means such as suction cups, the equipment can bemoved in a relatively free manner. However, provision of a room withsuch a structure for the equipment causes a significant problem in viewof the associated expenses, and failure tends to occur in theair-conditioning under the floor because of the complicated underfloorstructure. Moreover, it is well known that such a system cannot beapplied to equipment already installed because it requires modificationsto the entire room.

OBJECTS OF THE INVENTION

It is one object of the present invention to provide an aseismic supportstructure which prevents the equipment from falling down or moving whenan earthquake occurs. In addition, it is another object to provide anaseismic support structure which has an earthquake resistance of 1 G ormore and which can withstand the impact of an earthquake on theequipment at the minimum level.

It is another object of the present invention to provide an aseismicsupport structure and system which does not require any modifications toa room in which the equipment is installed, is easily applicable toexisting equipment, eliminates the complexity of the underfloorstructure and does not cause any harm in relocation of the equipment.

SUMMARY OF THE INVENTION

The present invention is directed to an aseismic support structure whichsecures equipment by fixing one end to a fixed floor and another end tosubject equipment to be installed on a free access floor. The aseismicsupport structure of the present invention includes a toggle bar with apredetermined length and extendable, preferably in the longitudinaldirection. The toggle bar has a universal joint at each end and theuniversal joint allows the toggle bar to uniformly incline at anyorientation parallel to the fixed floor. An attachment mechanism issecured to the toggle bar at one end through one of the universaljoints, having at another end a third universal joint provided with anaxis of rotation at least parallel to the floor surface, and constrainedfor its position to the floating floor. A cantilever is connected to theattachment mechanism by the third universal joint at one end and has afourth universal joint at another end. The cantilever extendssubstantially parallel to the fixed floor. A mounting mechanism isconnected to the cantilever through the fourth universal joint forsecuring the subject equipment. All of the universal joints typicallyinclude a horizontal rotation section freely rotatable around an axis ina direction perpendicular to the fixed floor surface (hereinafter calledthe "z direction") and a vertical rotation section freely rotatablearound an axis in a direction horizontal to the fixed floor surface(hereinafter called the "x direction").

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an aseismic support structure accordingto the present invention.

FIG. 2 is a side schematic view of the aseismic support structureaccording to the present invention.

FIG. 3 is a schematic view showing the attachment section and themounting section of the aseismic support structure according to thepresent invention.

FIG. 4 is an another embodiment of the attachment section and themounting section of an aseismic support structure according to thepresent invention.

FIG. 5 is a schematic view of a prior art vibration insulation floorsystem.

FIG. 6 is a perspective view of another embodiment of an aseismicsupport structure according to the present invention.

FIG. 7 a perspective view showing equipment secured to a fixed floor bythe aseismic support structure of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an embodiment of an aseismic support structure according tothe present invention. The aseismic support structure is secured to afixed floor 1 at one end with means such as bolts. In addition, it isconnected to equipment installed on a free access floor 2 extendingtherethrough with mounting means 12. This provides a function forsecuring the equipment on the fixed floor 1. A caster 10 shown in FIG. 1is usually mounted on the equipment and does not constitute a part ofthe present invention. Although the equipment is integral to the caster10, it is not shown in the figure.

FIG. 2 shows a schematic view of the aseismic support structure of FIG.1 viewed from one side. The aseismic support structure comprises atoggle bar section 6 which includes a toggle bar 4, an attachmentsection 8 extending through the free access floor 2, and a mountingsection 7 attaining connection with the equipment.

Referring to FIGS. 1 and 2, the toggle bar section 6 includes the togglebar 4, and universal joints 41 and 42 provided at each end of the togglebar 4. The toggle bar 4 is so constructed that a steel member isthreaded in at each end of its frame-like portion, allowing adjustmentof its entire length. The toggle bar 4 may have a structure whichincorporates a resilient member such as a spring, as required, toprovide a predetermined spring constant in the longitudinal direction.In such a case, a suitable spring constant ranges from 15 to 30 kgf/mm.The suitable spring constant is also a design factor depending on theweight of the subject equipment to be supported and how much earthquakeresistance is required. The spring constant may be adjusted by themodulus of elasticity and the sectional shape of materials constitutingthe toggle bar 4.

The universal joints 41 and 42 are connected to each end of the togglebar 4. In this embodiment, the universal joint is designed to be freelyrotatable in the horizontal and the vertical directions. The horizontalrotation is provided by a horizontal rotation section 5 rotating aroundan axis perpendicular to the fixed floor 1, while the vertical rotationis provided by a vertical rotation section 3 integral with thehorizontal rotation section and rotating around an axis in a directionparallel to the fixed floor 1. For the horizontal and vertical rotationsections, a combination of universal joints or flexible joints areemployed for allowing free rotation without resistance. It should beunderstood that the structure of universal joints 41 and 42 should notbe limited to the ones shown in FIGS. 1 and 2. It is sufficient that theuniversal joint has a structure which allows uniform inclination of thetoggle bar in any directions horizontal to the fixed floor. The presentinvention may be implemented by using a mortar-shaped structure similarto, for example, a human shoulder joint.

As shown in FIG. 3, the attachment section 8 mainly consists of a shaft9 with a predetermined length. The shaft 9 is connected to the togglebar 4 at one end through the universal joint 42. The other end of theshaft 9 is connected to the mounting means 7 through the universal joint43. When the aseismic support structure secures the equipment, theattachment section 8 is at a location where it extends through the freeaccess floor 2, and its position in the direction parallel to the floorsurface is constrained. The shaft 9 preferably has high rigidity, and isnot easily deformed by the vibration of an earthquake. Although aconsiderable space is provided between the shaft 9 and the free accessfloor 2 in FIG. 3, the space is not necessarily required. However, somedegree of freedom is necessary not to prevent circumferential rotationof the shaft 9. A filler 18 is fixed on the shaft 9 in such a mannerthat it just slightly contacts the free access floor. The filler 18consists of a steel section 17 and a rubber section 16. The rubbersection has a high vibration insulation capability, and serves to absorbthe vibration of an earthquake. The rubber section 16 preferablyconsists of a material with good weather resistance such as chloropreneor butyl rubber.

The mounting section 7 serves to connect the aseismic support structureto the equipment. The mounting section 7 is connected to the shaft 9through the universal joint 43. The universal joint 43 need not have ahorizontal rotation section as in other universal joints 41 and 42. Amain component of the mounting section 7 is a mounting mechanism 12. InFIGS. 1 and 3, the mounting mechanism 12 presents a frame shape intowhich the caster 10 mounted on the equipment is fitted. Other approachescan be used for mounting the equipment on the mounting section 7. Forexample, as shown in FIG. 4, a shaft 15 of a wheel 14 of the caster 10may be directly inserted into the mounting mechanism 12. Requirementsfor the mounting section 7 include firmly securing the wheel 14 of thecaster on the free access floor 2.

The operation of the aseismic support structure according to the presentinvention will now be described. For the purpose of this description,the longitudinal direction of the toggle bar 4 is the z direction shownin FIG. 2, a direction perpendicular to it and also perpendicular to thesurface of paper sheet is the y direction, and the remaining directionis the x direction. An earthquake is comprised of three-dimensionalvibrations. In other words, it is a three-dimensional variation of adistance between two points. Now, if it is assumed, as shown in FIG. 2,that a connection point between the fixed floor and the equipment ispoint A, a contact point between the free access floor and the aseismicsupport structure is point B, and a location where the equipment ismounted is point C, the relative positional relationship between pointsA and B varies in all of x, y and z directions with considerableacceleration at occurrence of an earthquake. The aseismic supportstructure is necessary to allow such variation in the positionalrelationship while absorbing its effects.

The positional variation of the toggle bar between points A and B in thelongitudinal direction (mainly, in the z direction) is absorbed by theelasticity provided for the toggle bar. Simultaneously, vibration whichmay be defined as continuous fine variations of position can be absorbedby setting the spring constant of the toggle bar to a suitable value.Even if the spring is not incorporated in the toggle bar 4 so that thepredetermined modulus of elasticity is not provided, or when the amountof displacement by an earthquake is small, the positional variation inthe z direction can be absorbed by, for example, the deformation of therubber section 17 in the filler 18 or the play in the universal joint.The positional variation in x and y directions can be absorbed by thesynergism of the horizontal and vertical rotations of the universaljoints 41 and 42. That is, the horizontal rotation sectioninstantaneously rotates in the direction in which the vibration occursso that the toggle bar 4 can incline around the axis of the verticalrotation section, and thus causes the direction to which the toggle bar4 can incline to match the direction of vibration by the earthquake.This principle allows it to follow up the vibration by the earthquake.

For vibration in the x direction, for example, as shown in FIG. 2, thetoggle bar 4 can incline to the x direction, and can follow up thevibration of an earthquake because the toggle bar can incline withoutrotation of the horizontal rotation section. If a component in the ydirection is added to the vibration, the horizontal rotation section ofthe universal joint rotates by that amount so that the toggle bar canincline in the direction of vibration. If the follow-up ability is notgood for the rotation in the horizontal direction, the toggle bar 4 issubject to a bending stress in the direction to which the toggle barcannot incline, and deformed so that its function would be lost.Accordingly, to improve the follow-up capability of the horizontalrotation section, measures are taken such that the joint section isconstituted by a combination of flexible joints or universal joints.

It is desirable that the positional relationship between points B and Cis constant. The shaft 9 has a property close to a rigid body which isnot easily deformed. In other words, the shaft 9 always stands verticalwith respect to the free access floor. Then, it only allows according tovertical vibration of an earthquake the universal joint 43 to rotatearound the horizontal axis, and the caster to bounce on the free accessfloor. The horizontal rotation of the mounting section 7 is provided bythe horizontal rotation section of the universal joint 42. However,there is no problem in providing another horizontal rotation section forthe universal joint 43.

Thus, the aseismic support structure according to the present inventionprovides can absorb three dimensional vibrations in x, y and zdirections by the toggle bar section 6, as well as the universal joints41 and 42 connected thereto.

FIG. 6 shows another embodiment of an aseismic support structureaccording to the present invention. In this embodiment, a cantilever 85is substantially parallel to the fixed floor between the attachmentmeans section 8 and the mounting section 7 of the aseismic supportstructure according to the first embodiment. The cantilever 85 serves tooffset the horizontal position of the mounting section 7 from a positionjust above a connecting section 90 with the fixed floor 1. In thisembodiment, effects provided by the toggle bar section 6 and theattachment means section 8 are same as those in the first embodiment.The attachment means section 8 is connected to one end of the cantilever85 by the universal joint 43. The other end of the cantilever 85 isconnected to the mounting section 7 by another joint 82. The universaljoints 43 and 82 are connected to the cantilever 85 through suitablefixtures 83 and 84.

FIG. 7 is a schematic view showing equipment 100 secured on the fixedfloor by using the second embodiment. The equipment 100 is connected tothe aseismic support structure through the mounting section 7. Theaseismic support structure is connected to the fixed floor 1 at an end90 different from the end where the mounting means section 7 exists.This embodiment is characterized by the mounting means section 7 notbeing positioned just above a connection point 90 connecting the togglebar section 6 with the fixed floor 1. The cantilever 85 is disposedbetween the mounting means section 7 and the toggle bar section 6, andextends substantially parallel to the fixed floor. The reason why themounting means section 7 needs to be offset from a position just abovethe connection point 90 lies in, for example, that wiring may be crowdedat a position 101 just below the equipment 100 so that the toggle barsection 6 may not necessarily be positioned just below the equipment100. That is, the cantilever 85 provides an advantage that it preventsthe connection point 90 from being positioned just below the equipment100 so that the aseismic support structure can be installed regardlessof the conditions just below the equipment 100.

The cantilever 85 should have sufficient rigidity such that it is notdeformed by the weight of the equipment and shock from an earthquake. Inaddition, the cantilever 85 is also not limited to a specific length aslong as it satisfies the required rigidity. Such rigidity and length aremerely matters of design.

The aseismic support structure according to the present invention cansecure the equipment on the fixed floor. Accordingly, it has advantagesof the direct support system preventing falling-down and movement, andalso has a feature not to directly transmit the vibration of anearthquake to the equipment by providing elasticity for the toggle baror employing a vibration absorber for the interposed filler. Thus, itcan attain the target of earthquake resistance of 1 G or more.

Furthermore, the aseismic support structure according to the presentinvention can provide earthquake resistance for the equipment only byconnecting one end to a part of equipment placed on the free accessfloor and another end to the fixed floor. That is, it can very easilyattain the aseismic effect in view that it does not require modificationwork for the room as in the conventional vibration isolation system inattaining the earthquake resistance. Furthermore, since it can berelatively easily removed, it can easily be relocated with the equipmentand can be easily installed on the existing equipment.

In addition, the aseismic support structure of the present invention canbe installed regardless of the conditions just below the equipment byproviding between the toggle bar section and the mounting section acantilever 85 extending substantially parallel to the fixed floor asdisclosed in the embodiment of FIGS. 6 and 7. Accordingly, measuresagainst an earthquake can be further easily provided while maintainingthe existing installation conditions.

The description provided above for the present invention assumes a casewhere electronic equipment such as a computer is installed on theaseismic support structure. However, manufacturing facilities such as achemical plant requires similar considerations. Since chemicalmanufacturing facilities can cause a serious impact not only to humansbut also to the surrounding environment if they are destroyed, it isnecessary to prevent such a situation whenever possible. Accordingly,the installation of the aseismic support structure according to thepresent invention covers all equipment requiring measures against anearthquake and particularly those installed on a floating floor. It isnot limited to electronic equipment such as a computer as disclosed inrelation to the embodiments.

While the invention has been particularly shown and described withrespect to preferred embodiments thereof, it should be understood bythose skilled in the art that the foregoing and other changes in formand detail may be made therein without departing from the spirit andscope of the invention as defined in the appended claims.

What is claimed is:
 1. An aseismic support structure having a first endsecured on a fixed floor and a second end connected to a subjectstructure placed on a floating floor, said aseismic support structurecomprising:a toggle bar having a first universal joint at its first endand a second universal joint at its second end, said first and seconduniversal joints allowing the toggle bar to rotate horizontally aroundan axis perpendicular to said fixed floor and to rotate verticallyaround an axis parallel to said fixed floor; an attachment sectionconnected to said first universal joint by said second universal jointat one end, and having a third universal joint at another end, saidattachment section position horizontal to said fixed floor and beingconstrained to said floating floor; a cantilever connected to saidattachment section by said third universal joint at one end, and havinga fourth universal joint at another end, said cantilever extendingsubstantially parallel to said fixed floor; and a mounting sectionconnected to said cantilever through said fourth universal joint, saidsubject structure being secured on said mounting section.
 2. An aseismicsupport structure according to claim 1, wherein said toggle bar has aspring constant of 15-30 kgf/mm.
 3. An aseismic support structureaccording to claim 1, wherein said toggle bar comprises a mechanism foradjusting its length.
 4. An aseismic support structure according toclaim 1, wherein said first and second universal joints comprise ahorizontal rotation section freely rotatable around an axis in adirection perpendicular to said fixed floor surface and a verticalrotation section freely rotatable around an axis in one directionhorizontal to said fixed floor surface.
 5. An aseismic support structureaccording to claim 1, wherein said first universal joint is directlysecured on said fixed floor.
 6. An aseismic support structure accordingto claim 1, wherein said fourth universal joint is not positioned justabove said first end by said cantilever.